(1) Field of the Invention
The present invention relates in general to data communication and power transmission systems, and more specifically to a wireless data communication and power transmission system for use with a network of sensing devices.
(2) Description of the Prior Art
Sensor technology in the broad sense involves measurements of a variety of physical phenomena. Sensing devices exist which can measure thermal energy, radiant energy, acoustic energy, air pressure, water pressure, velocity, acceleration, chemical concentrations and so on. Often these devices are able to detect phenomena far beyond human sensing capabilities.
Sensing devices are indispensable for allowing human travel through certain environments. In the harsh undersea environment, for example, sensing devices provide “sight” and “hearing” to undersea vehicles. Sensor measurements are used to aid underwater vehicles in navigation and in detection of other objects in the surrounding sea. Underwater vehicles, particularly large submarines, use a variety of sensing devices electrically wired and attached to the exterior of their hulls. There is, however, an ever-increasing demand for greater sensing capabilities for underwater vehicles. Underwater vehicles need a heightened awareness of their surrounding environment in order to perform the ever-demanding tasks expected of them. To meet this need underwater vehicles must employ more sophisticated and more sensitive sensing devices and must employ them in larger numbers on a much greater scale than now used. Current methods, however, do not address the various constraints involved in implementing a very large sensor network for underwater vehicles. Underwater vehicles are constrained by the size of the sensing devices and the available space on the hull exterior. A significant increase in the number of sensing devices would increase the overall weight of an underwater vehicle. It would affect the construction methods used in building the underwater vehicle, and alter the structural design of the underwater vehicle. More sensors would also require increased power expenditures, an increase of bundled wiring and a complex addressing and communication system to monitor the multitude of sensing devices.
Use of sensing devices that are drastically reduced in size alleviates several of the above-mentioned constraints such as available space, weight, shape and power consumption. There currently exist Micro Electronic Mechanical Systems (MEMS) sensors that are significantly smaller than the sensors commonly used on the exterior of underwater vehicles. MEMS devices are an integration of mechanical elements and electronics on a common substrate such as silicon. The electronics are fabricated using integrated circuit (IC) process sequences. The micro-mechanical components are fabricated using compatible “micro-machining” processes that selectively etch away parts of the substrate (e.g., silicon wafer) or add new structural layers to form the mechanical and electromechanical devices. MEMS sensing devices have low power consumption, are smaller, more functional, lighter, more reliable and are produced at a fraction of the cost of conventional macro-scale devices.
Use of MEMS sensing devices allows for sensor networks on the order of 106×106 arrays of sensing devices arranged over the exterior of a underwater vehicle's hull. Powering such a large sensor network and communicating with the network using the conventional method of conductive wire bundles is overly complicated from both a design and a maintenance perspective, not to mention cost prohibitive.
U.S. Pat. No. 6,208,247 to Agre et al, for “Wireless Integrated Sensor Network Using Multiple Relayed Communications” (issued Mar. 27, 2001) teaches a sensor network that employs miniature sensors in wireless communication. The invention is used in a large network of wireless nodes dispersed over a distance of 100 yards. The nodes are self contained battery powered miniature electronic sensing stations adaptable for two way wireless communication. The aforementioned patent, while offering valuable information, does not by itself address the need for a wireless power transmission and communication network of low power sensors. It does not incorporate wireless power transmission, but rather relies on batteries to provide power to the sensing stations. Furthermore it is not adaptable to an underwater environment.
There is currently no apparatus for efficient, cost effective powering and communicating with a large array of MEMS sensors. What is needed is a wireless power transmission and communication network that can interrogate and power sensors for use on an underwater vehicle.